We propose to pilot test a universal program developed to enhance family protective factors near the end of elementary school, thereby buffering children from the elevated risks of substance use and associated problems that will soon emerge in early adolescence. The proposed program is designed to strengthen family relationships through a focus on the sibling relationship and will be delivered in elementary schools to groups of sibling dyads beginning when the older sibling is in fifth grade and the younger sibling is one to three years younger (the modal age spacing for siblings in the U.S. is two to three years). This innovative program combines the power of family intervention with the universal context of the elementary school and a non-stigmatizing family focus on sibling relationships. The pilot will be conducted in rural and semi-rural school districts because rural youth have equal or higher levels of substance use compared to other youth, and research on rural substance use has lagged behind that in other contexts. Moreover, given the relative lack of other opportunities and geographic distances, siblings in rural areas can be especially important influences on each other. PUBLIC HEALTH RELEVANCE: This project seeks to test an innovative family-focused intervention focused on sibling relationships, as well as parent management of sibling relations. Siblings influence each other's substance use and other problem behaviors to a substantial degree. The program would improve sibling relationships in order to decrease the development of negative and coercive behaviors, which then lead to association with antisocial peers. Developing and disseminating new, effective preventive programs such as the one proposed would have substantial public health benefits for individuals, families, and society.